1. Field of the Invention
This invention relates generally to improvements in propeller systems for developing a propulsive force, and more particularly, it pertains to a new method and apparatus for propelling watercraft, such as boats, ships, ferries, rafts, fish-boats, dredges, tankers, tug-boats, etc.
2. Description of the Prior Art
Nowadays, the most common means for propelling watercraft is the screw type propeller wherein the axis of rotation of the blades is disposed along the advancement direction of the vehicle. The screw propellers displace the water as a result of orientation of the blades with angles of incident relative to the advance direction. Only the rearward component of the velocity of advance direction, they have to be rotated in water with very high speed to develop a sufficient propulsion force. As a result, much of the energy is wasted on rotation of water with formation of water disturbances such as visible wakes, vortices, cavitation, etc. That is why efficiency of the screw propellers is low, especially when they are used for propelling many types of heavy boats and ships. They have a very limited optimum range.
To improve such disadvantageous aspects of the screw propellers, various propulsion apparatus have been developed throughout the years with a transversely disposed axes of rotation of the blades (vertical or horizontal) for developing more effective propulsion force with lower speed of rotation. Numerous patents and researches have been devoted to development of propeller systems wherein the propeller blades are pivoted simultaneously with rotation of the driving shaft and to the problem of optimizing the cyclic variations of the orientation of individual blades. Some of such systems utilize rotation of propeller blades or paddles not only around the axis of the driving shaft but also around complementary axes of rotation. The basic concept presented in these systems is that the usable propulsive force is developed as a result of rotating the blades around two axes of rotation with variable orientation of the rotated blades relative to the driving shaft.
Propulsion apparatus are known (U.S. Pat. Nos: 1,284,282 to Fitzpatrick, 1,450,454 to Roney, 1,667,140 to Clark, 1,923,249 to Abram) wherein blades of feathering type extend radially from the of the paddles has a pair of perpendicular to each other blades driving shaft and are rotated around radial axes simultaneously with rotation of the driving shaft. In the paddling position, the blades are held in a plane parallel to the axis of the driving shaft and in the feathering position, the blades are held in a plane perpendicular to the axis of the driving shaft. A serious drawback of such systems is that, in the process of changing from one position to the other, the blades have to be rotated 90 degrees around their longitudinal axes with a considerable resistance of the fluid and low paddling and propulsion efficiency during such rotation.
There are also known propulsion apparatus wherein the propeller blades are oriented and rotated in the planes parallel to the driving shaft (U.S. Pat. No. 3,270,820 to Frazier, British patent No. 217,223 to Pensovecchio). Although having advantages in respect to the propellers with feathering blades, such apparatus with only two blades mounted in a plane perpendicular to the propeller shaft also have low efficiency and irregular power consumption. Different combinations of such propulsion apparatus are cumbersome and the mechanisms employed to effect their operations is complicated. For these reasons, a limited practical success has been obtained by such type of apparatus.
Another disadvantage of the conventional screw propellers is their vulnerability to underwater impact and damage when they are used in shallow water or in situations when there are different kinds of submerged debris such as tree logs, limbs, etc. In most cases the conventional screw propeller cannot be raised sufficiently to enable the craft to be beached.
To solve this problem, the screw propeller can be mounted on the watercraft in such a position that a portion of the propeller blades rotate out of the water, as described, for example, in U.S. Pat. No. 5,807,151 to Sumino. However, such a mounting of the screw propellers considerably reduces their propulsion efficiency. As a result, the usage of such water surface-piercing screw propellers remains restricted.
Different types of paddle-wheels which are used for propelling watercraft in shallow water or in the water containing dangerous debris, as disclosed, for example, in U.S. Pat. No. 6,264,518 to Price and U.S. Pat. No. 6,447,352 to Nuss, also provide very low propulsion efficiency, speed and maneuverability for the watercraft.
The present invention seeks to overcome the deficiencies of known propulsion systems and to benefit from the advantages that may be expected from the new method and apparatus.
The object of the invention is to provide a reliable propelling apparatus with a transversely disposed driving shaft and improved propulsion efficiency for different types of the watercraft.